Jun Zhang,Jianan Li,Guoliang Jia,Yikun Jiang,Qinyi Liu,Xiaoyu Yang,Su Pan
To engineer bone tissue, an ideal biodegradable implant should be biocompatible, biodegradable, osteoinductive and osteoconductive. However, the lack of bioactivity has seriously restricted the development of biodegradable implants in bone tissue engineering. In this study, we have developed a three-dimensional porous poly(L-lactic-co-glycolic acid)/hydroxyapatite (PLGA/HA) scaffold based on the dual delivery of bone morphogenic protein 2 (BMP-2) and insulin-like growth factor 1 (IGF-1) via polydopamine (PDA) coating. The aim of this study was to improve the osteoinductivity of biodegradable implants for clinical bone repair via a PDA-assisted BMP-2 and IGF-1 surface modification strategy. Our study demonstrated that PDA layer surface modification could more efficiently immobilize BMP-2 and IGF-1 on the scaffold surfaces than physical adsorption, and the immobilized growth factor was released slowly and steadily from the scaffold in a sustained manner. MC3T3-E1 cell attachment and proliferation on IGF-1 and BMP-2-immobilized porous scaffolds were much higher than other groups. According to an in vitro osteogenesis assay, alkaline phosphatase (ALP) activity, the expression of osteogenesis-related genes and the mineralization capacity of MC3T3-E1 cells were increased by the incorporation of BMP-2 and IGF-1. In vivo, digital radiograph evaluation demonstrated that there was the most rapid healing in the defects treated with the IGF-1 and BMP-2 immobilized porous scaffold compared with the other groups eight weeks after implantation. In vitro and in vivo results of this study revealed that the PDA-assisted surface modification method can be a useful tool to graft biomolecules onto biodegradable implants, and the dual release of BMP-2 and IGF-1 could promote cell proliferation and osteogenesis differentiation. Based on the results, the surface modification strategy with growth factors has great potential for the enhancement of osteointegration of biodegradable bone implants.
Poly(lactic-co-glycolic acid) (PLGA) and hydroxyapatite (HA) are considered potential osteoinductive materials because of their biodegradability and mineralization features. However, the hydrophobicity of scaffold surfaces is less supportive of cell attachment and proliferation because of poor wettability. The mode of binding of growth factors to the scaffold also affects cell differentiation into osteoblasts. The half-life of a growth factor in vivo can be increased by binding the factor to the scaffold surface. In this work, we prepared a porous PLGA/HA scaffold grafted with recombinant human bone morphogenic protein-7 (rhBMP-7) attached via polydopamine (pDA) for bone repair. The pDA coated PLGA/HA (pDA-PLGA/HA) scaffolds were characterized by energy dispersive X-ray analysis and Fourier-transform infrared spectroscopy. The microstructure and porosity of PLGA/HA scaffolds were analyzed by scanning electron microscopy and micro-computed tomography. The release profile of rhBMP-7 grafted onto the pDA-PLGA/HA (pDA-PLGA/HA/BMP-7) scaffolds was examined for 21 days. The attachment efficiency, cell proliferation rate, alkaline phosphatase activity, calcium deposition, and osteoblast-related gene expression of bone marrow-derived stem cells to PLGA/HA, pDA-PLGA/HA, and pDA-PLGA/HA/BMP-7 scaffolds were evaluated. To assess the ability of bone repair in vivo, scaffolds were implanted into critical-sized calvarial defects created in mice, and the in vivo tissue-engineered bone was monitored by micro-computed tomography and histology. In vivo experiments revealed rapid healing of the defects treated with the pDA-PLGA/HA/BMP-7 scaffolds compared with pDA-PLGA/HA and PLGA/HA scaffolds at week 8 post-surgery. These results collectively demonstrate that the rhBMP-7-immobilized PLGA/HA scaffold via pDA is a promising candidate for calvarial repair.
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